Will a MK1 Hardtop fit a MK2?

Yes, the top will physically fit but Mazda state that the side seals changed with the introduction of the MK2 and issued a bulletin saying that they require changing “to prevent wind noise & water leaks” (part numbers - NC10-R1-881D & NC10-R1-891D). In reality I don’t think they give any trouble if left as they are. One thing you will have an issue with is the wiring harness that connects the HRW to the vehicle loom. The multi-plug is different on the MK2 to that on the MK1 so you will need to buy a new one of those (Mazda part number NC11-R1-060A) it’s no trouble to change it.